1. Field of the Invention
This invention relates generally to tools used to complete subterranean wells and more particularly relates to apparatus and methods for use in performing gravel pack operations.
2. Description of Related Art
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production of oil and gas can begin.
Sand or silt flowing into the wellbore from unconsolidated formations can lead to an accumulation of fill within the wellbore, reduced production rates and damage to subsurface production equipment. Migrating sand has the possibility of packing off around the subsurface production equipment, or may enter the production tubing and become carried into the production equipment. Due to its highly abrasive nature, sand contained within production streams can result in the erosion of tubing, flowlines, valves and processing equipment. The problems caused by sand production can significantly increase operational and maintenance expenses and can lead to a total loss of the well.
One means of controlling sand production is the placement of relatively large sand (i.e., xe2x80x9cgravelxe2x80x9d) around the exterior of a slotted, perforated, or other type liner or screen. The gravel serves as a filter to help assure that formation fines and sand do not migrate with the produced fluids into the wellbore. In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the unconsolidated formation that is to be completed for production. The screen is typically connected to a tool that includes a production packer and a cross-over, and the tool is in turn connected to a work or production tubing string. The gravel is mixed with a carrier fluid and is pumped in a slurry down the tubing and through the cross-over, thereby flowing into the annulus between the screen and the wellbore. The carrier fluid in the slurry leaks off into the formation and/or through the screen. The screen is designed to prevent the gravel in the slurry from flowing through it and entering the production tubing. As a result, the gravel is deposited in the annulus around the screen where it forms a gravel pack. It is important to size the gravel for proper containment of the formation sand, and the screen must be designed in a manner to prevent the flow of the gravel through the screen.
A problem that is frequently encountered in a gravel pack completion, especially in long or highly deviated sections, is the formation of gravel bridges in the annulus between the wellbore and the tubing string. Non-uniform gravel packing of the annulus between the screen and the wellbore often occurs as a result of the premature loss of carrier fluid from the slurry. The fluid can be lost into high permeability zones within the formation, leading to the creation of gravel bridges in the annulus before all the gravel has been placed. These gravel bridges can further restrict the flow of slurry through the annulus, which can result in voids within the gravel pack. Once the well is placed on production, the flow of produced fluids will be concentrated through any voids in the gravel pack, which can result in the migration of fines and sand into the produced fluids and lead to the problems discussed above.
There is a need for improved tools and methods to avoid premature dehydration of the gravel pack slurry and minimize the creation of gravel bridges and voids during a gravel pack completion of a wellbore.
This invention provides improved apparatus and methods for completing a subterranean zone penetrated by a wellbore.
One embodiment of the invention is an apparatus comprising a tubular member having a wall and a longitudinal bore. There are a plurality of radial apertures through the tubular member wall, the apertures defining at least one radial arc and creating at least one perforated radial aperture zone and at least one non-perforated radial blank zone. A screen member is attached to the exterior of the tubular member that covers the apertures. The screen member can comprise a filtering mechanism that will prevent the passage of gravel particulate matter while allowing the communication of fluids. The screen member can comprise a filtering mechanism such as a continuous wire wrapped in a spiral configuration, a plurality of elongate bars spaced longitudinally about the exterior of the tubular member, a wire mesh, or a slotted sleeve element. Any of these embodiments can also include a spacer that forms a fluid flow annulus between the screen member and the tubular member apertures. The screen member can be located within the radial arc of the tubular wall in which the apertures are located. The screen member can enclose the radial arc of the tubular member wall in which the apertures are located. The placement of the radial blank zone into the wellbore can create an annular flow region. The tubular member can further comprise an offset device to enable the eccentric placement of the sand screen within the wellbore. The eccentric placement of the sand screen within the wellbore can create an annular flow region.
An alternate embodiment of the invention consists of a sand screen that comprises a base tubular having at least one perforated radial aperture zone and at least one non-perforated radial blank zone and a screen attached to the base tubular that covers the radial aperture zone. The screen can comprise apertures that allow fluid to pass therethrough, but are small enough to prevent the flow of a gravel particulate. The screen can comprise a filtering mechanism such as a continuous wire wrapped in a spiral configuration, a plurality of elongate bars spaced longitudinally about the exterior of the tubular member, a wire mesh, or a slotted sleeve element. The sand screen can further comprise an offset device to enable the eccentric placement of the sand screen within a wellbore. The eccentric placement of the sand screen within the wellbore can create an annular flow region.
Another embodiment is a well completion comprising a production tubing having at least one sand screen in fluid communication with the production tubing. The sand screen can comprise a base tubular having at least one perforated radial aperture zone and at least one non-perforated radial blank zone and at least one screen attached to the base tubular that covers the radial aperture zone. The screen comprises apertures that allow fluid to pass but are small enough to prevent the flow of a gravel particulate. The screen can comprise a filtering mechanism such as a continuous wire wrapped in a spiral configuration, a plurality of elongate bars spaced longitudinally about the exterior of the tubular member, a wire mesh, or a slotted sleeve element. The sand screen can further comprise an offset device to enable the eccentric placement of the at least one sand screen within a wellbore. The eccentric placement of the sand screen within the wellbore can create an annular flow region.
Yet another embodiment is a well completion comprising a wellbore casing with at least one perforation, the perforations being located around the circumference of the casing by a perforation phasing and orientation. The well completion includes a production tubing having at least one perforated radial aperture zone and at least one non-perforated radial blank zone and the production tubing is positioned within the wellbore creating an annular flow region. The production tubing can further comprise a screen element that covers the perforated radial aperture zone. The perforations in the wellbore casing can be selectively placed by controlling the perforation phasing and orientation. The radial aperture zone and the radial blank zone can be created by selectively perforating the production tubing. An annular flow region can be created by aligning the radial aperture zone and the radial blank zone with the perforations of the wellbore casing. An annular flow region can also be created by positioning the production tubing in an eccentric location relative to the wellbore casing. The radial aperture zone can be radially aligned with perforations of the wellbore casing.
A further embodiment of the present invention is a method of completing a well by providing a sand screen in the well and creating an annular flow region adjacent to the sand screen. The method can further comprise perforating the wellbore casing in a predetermined phasing arrangement to create well perforations, providing at least one non-perforated radial blank zone of the sand screen, and orienting the radial blank zone relative to the well perforations. An annular flow region can be created by positioning the sand screen in an eccentric location relative to the wellbore casing. An annular flow region can also be created by aligning the sand screen in relation to the wellbore casing perforations such that the radial blank zone is not adjacent to a well perforation.
Yet another embodiment is a method of completing a wellbore that includes placing within the wellbore to be completed: (i) an apparatus that comprises a tubular member having a wall and a longitudinal bore, (ii) at least one aperture through the tubular member wall, the at least one aperture defining at least one radial arc and creating at least one perforated radial aperture zone and at least one non-perforated radial blank zone, and (iii) a screen member attached to the exterior of the tubular member that covers the apertures. A fluid comprising gravel particulate matter is injected into the annulus between the wellbore and tubular member, whereby the gravel particulate matter is placed within the annulus between the tubular member and the wellbore wall. The screen member can comprise a filtering mechanism that will prevent the passage of gravel particulate matter while allowing the communication of fluids therethrough. The wellbore can have a cylindrical casing having a plurality of radial perforations, and the method can further comprise positioning the apparatus such that the apertures of the tubular member are radially aligned with the wellbore perforations. An annular flow region can be created by positioning the tubular member in an eccentric location relative to the cylindrical casing.
In still another embodiment a method of completing a wellbore that comprises a cylindrical casing is claimed. The method comprises perforating the casing with at least one perforation, the perforations being located around the circumference of the casing by a perforation phasing. An apparatus is placed within the wellbore that comprises: (i) a tubular member having a wall and a longitudinal bore, (ii) at least one aperture through the tubular member wall, the at least one aperture defining at least one radial arc and creating at least one perforated radial aperture zone and at least one non-perforated radial blank zone, and (iii) a screen member attached to the exterior of the tubular member that covers the apertures. The apparatus is positioned such that the apertures of the tubular member are radially aligned with the wellbore perforations. A fluid comprising gravel particulate matter is injected into the annulus between the wellbore and tubular member whereby the gravel particulate matter is placed within the annulus between the tubular member and the wellbore wall.
The radial apertures through the wall of the tubular member define a radial aperture zone with an aperture zone midpoint and a radial blank zone with a blank zone midpoint. The apparatus can be aligned in relation to the wellbore perforations such that the blank zone midpoint is not adjacent to a wellbore perforation. The apparatus can also be aligned in relation to the wellbore perforations such that the radial distance between the blank zone midpoint and the nearest wellbore perforation is maximized. An annular flow region can be created by positioning the tubular member in an eccentric location relative to the cylindrical casing.